1. Field of the Invention
This invention relates generally to telecommunications, and, more particularly, to wireless communications.
2. Description of the Related Art
In the field of wireless telecommunications, such as cellular telephony, a system typically includes a plurality of base stations (e.g., Node Bs) distributed within an area to be serviced by the system. Various Access Terminals (ATs, also known as User Equipment (UE), mobile devices, and the like) within the area may then access the system and, thus, other interconnected telecommunications systems, via one or more of the base stations. Typically, an AT maintains communications with the system as it passes through an area by communicating with one and then another base station, as the AT moves. The AT may communicate with the closest base station, the base station with the strongest signal, the base station with a capacity sufficient to accept communications, etc.
Communications between the ATs and the base stations may occur over a variety of channels, including dedicated and shared channels. Typically, when an AT is not currently involved in a communication session, it enters an idle mode of operation where the dedicated channels are dropped and it monitors only a shared channel to periodically determine if the base station is attempting to contact it. For example, in a wireless data technology known as High Rate Packet Data (HRPD), a control channel protocol provides a mechanism for an access network to deliver broadcast, multicast and unicast messages to idle and active ATs. The synchronous control channel is typically used to carry overhead messages, multicast and unicast messages (e.g., paging signals) to idle ATs. Currently, the forward link employs a 4-slot interlace structure, and the synchronous control channel can only use one of the 4 interlaces. Therefore, the maximum capacity of the synchronous control channel is 25% of the total forward link slots.
However, synchronous control channel usage has increased dramatically such that the 25% usage rate has become problematic. For example, with more applications (such as VoIP, PTT, Video Telephony) being employed in HRPD systems, control channel usage has increased significantly. Delivery of Page messages introduces very heavy traffic on the synchronous control channel. Additionally, for many attractive applications (such as, emergent notifications, community services, targeted advertisements, etc.), it is very fast, flexible and efficient to deliver short multicast messages to a group of people over the synchronous control channel. Further, Data over Signaling protocol, introduced in HRPD Rev. A, allows short data burst to be encapsulated in signaling messages and delivered over the synchronous control channel. Therefore, it becomes highly probable that the 25% usage rate of the forward link slots will be insufficient to accommodate all the traffic on the synchronous control channel.